Electronics Fundamentals

I was looking for an option to create a circuit with a switch, so I can use two single cell li-on Nokia cell phone batteries in series, but charge them in parallel through a USB charger. The idea is to be able to install the batteries in a small robot, where they will not be easily accessible to charge with my regular li-po battery charger. I have a couple of these simple but effective battery chargers lying around, but they can only charge a single cell. After some digging around, I found the following circuit and was able to successfully to put it together and test it. You need a “double-pole-double-throw” (DPDT) switches. It is a switch with six pins, essentially two single switches with a common button / slider. The two sides of the switch are not connected and control two separate circuits. So here is what you need: ...

This is a side project from my endeavor to program an Arduino Uno wirelessly (over Bluetooth) using a cheap HC06 JY-MCU Blueetooth Module I got from eBay. In order to kick off the Arduino bootloader and upload a new sketch, you need to reset the Arduino at the right moment, and hold the reset pin “LOW” for the right duration, or else things can go bad. Eventually I found out a circuit that does exactly what I wanted and, as a bonus, has a cool name: a “monostable multivibrator”. I feel smarter just typing that! ...

“It is good to have an end to journey toward; but it is the journey that matters, in the end.” ― Ernest Hemingway A few days ago my son came back from school with something that he had build in a Tech-Ed class. You had to carry a copper ring across a maze made of wire without “waking up the monster”. If you touch the wire, closing the circuit, the eyes (LEDs) would light up. ...